Special purpose chuck



, Oct. 7, 1947.

w. MASSI'ERER 2,428,375

SPECIAL PURPOSE CHUCK Filed May 15, 1945 II /a git/0W WALTER; MASSIERER c1 CGW W.

Patented Oct. 7, 1947 UNITED STATES ATENT OFFICE (Granted under the act of March 3,1883, as amended April 30, 1928; 370 O. G. 757) 1 Claim.

ing operations thereon and it has special reference to holding fixtures for glass lenses and other equivalent blanks that are to be acted upon by optical curve generators or other abrading machines.

Broadly stated, the object of my invention is to improve the design and extend the usefulness of optical blank holders of the type just named.

A more specific object is to make such holders adjustable and thereby enable them to receive blanks of varying diameters and thicknesses.

Another object is to incorporate mechanical ruggedness, ease of adjustment, and ease of assembly and disassembly' into holders of the type here considered.

A further object is to assure positive transmission of turning movement from the holder to the blank.

A still further object is to enable close curvature accuracy to be maintained during grindmg.

In practicing my invention I attain the foregoing and other objects and advantages by providing an adjustable chuck form of holding fixture that has the unique construction and the superior performance presently to be described. One preferred design for such'a fixture is shown by the accompanying drawing wherein:

Fig. 1 is a top plan view of the new chuck;

Fig. 2 is a section on line 22 of Fig. 1 showing the chuck with an optical lens blank held therein; and 5 Fig. 3 represents one of the chucks three segmental jaws as viewed from its inner side.

The improved adjustable chuck which these drawings illustratively show will be seen from Figs. 1-2 to comprise three radially movable jaws i=9 arranged as segments; a central adapter body or hub l2 supporting and imparting rotation to these jaws; and a collar l4 which encircles both the jaws and the hub and positions the jaws radially.

Also represented by Fig. 2 are a glass blank it held in position in'the chuck (for rotation 2 r with adapter l2) plus the lower spindle l8 (also shown by Fig. 1) of an optical grinding machine (not shown) of curve generator or other conventional type.

Such a machineis additionally provided with an upper spindle or grinding head (also not shown) which carries a diamond or other abrading tool positionable in contact with the upper surface of blank '16 and independently rotated by the upper spindle shaft. By shifting the grinding head tool along the arc of acircle that encompasses the lens blank, the desired optical curvature may be ground or gcnerated on the surface of blank l6.

Heretofore optical blanks of each different diameter have required an individual holder-which accurately matches that diameter; moreover, it has been customary, to allow the blank to rest loosely in the holder and to receive rotative motion solely from frictional contact with the holder. Since optical blanks to be ground typically have a wide 'variety' of difierent diameters, the number of conventional holders which must be provided often becomes objectionably large. Transfer of turning movement from the holder to the blank through frictional engagement only is, moreover, not always sulficiently positive to prevent slippage. Still further, the looseness of the blanks fit detracts from accuracy and objectionably alters ,the curvature.

The improved adjustable chuck type of holder here ently to be made evident.

The segments or jaws I!) of this chuck may satisfactorily be made of brass or other equiv-- alent metal. and either a. greater or'lesser num- A shoulder at the base of each jaws upstand-- ing gripping edge supports the under side of blank l6 as indicated by Fig.2; a slot 20 in each jaws underside fits over a torque transmitting pin 2! protruding from the upper face of adapter hub I2 (again see Fig. 2); and the outside of each jaw is tapered-as shown by Figs. 2-3'for disclosed overcomes all of these diiiiculties' and afiords additional advantages presmating contact with the internally tapered chuck adjusting sleeve M.

This adjusting sleeve 14 also may satisfactorily be made of brass or other equivalent metal. Its upper interior is tapered as represented, while its lower interior carries threads 22 on the outside of adapter body l2. The outside of this sleeve may be knurled (not shown) to facilitate rotation by an operator.

Turning of the sleeve with respect to the hub raises or lowers the sleeve on the adapter, depending upon the turning direction, and thereby either wedges all three jaws l inwardly towards the adapter hubs center or allows those jaws to be moved outwardly away from the center. The direction of threads 22 is such that grinding torque exerted on blank 1'6 tends to tighten rather than loosen wedging action by sleeve I4 on jaws I0. I

When screwed down to its lowermost position, moreover, the top of the sleeve clears the bottom of the jaws and permits complete withdrawal thereof from the adapter body. This makes assembly and disassembly of the chuck very easy.

This adapter body or hub l2 may satisfactorily be made of steel or other equivalent metal. Preferably it is designed iorremovable fit into a ma ing ly shaped recess in the grinding machines lower spindle l8, Reception of rotative motion from the spindle may be effected in any suitable manner, as through a, pin 23 carried by the spintile and fitting into a mating slot in the lower flange of the hub body.

The upper portion of adapter I2 is provided with the circumferential groove which Fig. 2 represents as accommodating lower mating lips on the three segmental jaws l8. Preierably the axial width of the groove is only slightly greater than the jaw lip thickness; freedom for radial movement of the jaws is, however, maintained in order that adjustability of the complete chuck may easilyand readily be effected.

- Other equivalent construction for the hub-like adapter'body l2 may, of course, be substituted.

One of these contemplates making the extreme upper portion of the body as a washer that is snacedly securedto the adapters lower portion by a central pin (not shown); another contemplates making the threaded part. 22 and the grooved. metal thereabove as a piece separate iromthe lower base of the adapter but secured thereto by a central rod-like extension (not shown): projected down into the base,

.11 The torque transmitting pins 21, earlier men tioned as interconnect'mg the jaws with the represented hub' 12', in no way impair the chucks adjustability, since the jaw slot 251 (see Fig. 3) that engages each pin allows tree radial sliding of the jaw H) over the pin. Other equivalent expedients for transmitting torque while allowing radial shifting of the jaws are, of course, useable. From the foregoing description of component parts the manner in. which the complete chuck functions will now have become apparent. screwing of the adjusting collar l4 upwardly on the threads 22 of the adapter radially wedges all three jaws lfi inwardly; screwing oi the collar downward-1y. on the adapter frees all of those jaws for outward radial movement away from the chucks center.

In the illustrative construction shown, the range ofsuch radial movement on the part of each jaw- Ill is slightly less than one eighth inch. This gives a total diametrica'l adjustment range of about three-sixteenths of an inch, T e i illustrated (drawings are to slightly reduced scale) is, therefore, capable of receiving optical blanks I5 whose diameters vary within the named range. In curvature the jaw faces preferably match the diameter that is represented by a mid positioning of the jaws.

To insert a blank l6 into the chuck it is only necessary to release and spread the jaws beyond that blanks diameter, place the blank between the jaws as shown in Fig. 2, and then wedge the jaws thereagainst by screwing collar [6 upwardly. The resulting engagement holds the blank firmly and accurately in the chuck and allows curvature grinding operations to be very accurately performed thereon without slippage or misalignment. Removal from the chuck is effected by screwing the collar 14 downwardly to allow movement of jaws l0 outwardly away from the blank.

The named positive securing of the blank in the chuck assures maximum curvature accuracy during grinding and it further imparts desirable resistance against tilting or tipping and thereby extends the thickness of blanks which are grindable in abrading machines of curve generator and other types. By reason, moreover, of the mechanical ruggedness of my improved chuck long life and high reliability are at once assured.

Although Ihave described'my adjustable chuck improvements by reference to' devices for rotating optical blanks during grinding or polishing, it will be apparent that such reference is illustrative rather than restrictive and that holding fixtures for other uses also may be benefited.

It will accordingly be seen that I have improved the. design and extended the usefulness of chucktype' holding deviceswhen considered generally; that I have impartedready adj-ustability to such holding fixtures and have enabled them to receive optical or other blanksoi varying diameters and thicknesses; that I haveincorporated mechanical ruggedness, ease of adjustment and ease of assembly and disassembly into such holders; that I have assured ositive transmission of turning movement from the holder to the blank; and that I have enabled close curvature accuracy to be maintained during grinding.

My inventive improvements are therefore extensive in their adaption and are not to be restricted to the specific form here disclosed by way of illustration. I

I claim:

In an adjustable chuck for holding optical blanks, the combination of a hub-like adapter comprising a base portion .for attachment to a spindle shaft plusan end portion which has a circumferential groove extending radially thereinto and which has external threads between that groove and said base-portion, a plurality of jaws spacedly placed around said adapters end and having inwardly-protruding lower base lips which fit into and are slidably engaged by said radial groove and eacltjawfurther having a slot that radially extendathrough the-entire underside of the jaw; a member carried by said adapter beneath each jaw and protruding upwardly from the'adapter for radially slidable engagement by the said slot in that jaw to thereby restrain the jawfrom rotative movement with respect to said adapter without interfering withradialmovement by the jaw, each of said jaws further having an upper flat peripheral seating surface perimetri- ,cally bounded by a mutually-'coactive inner gripping ,face spaced axially from said adapters end 755 and an outer wedging face which tapers out- 5 wardly from the jaws base to the jaws gripping edge, and a chuck adjusting sleeve encircling the adapters end portion and said jaws and having a tapered upper interior which mates with and bears against said outer jaw wedging faces, said sleeve also having threads at its lower interior which mate with and turnably engage said adapters external threads.

WALTER MASSIERER.

REFERENCES CITED The following references are of record in the file of this patent:

Number Number 6 UNITED STATES PATENTS Name Date Spaander Nov. 21, 1922 Clark Sept. 11, 1928 Bemis July '7, 1908 Ainsley Oct. 24, 1916 Cossman Mar, 4, 1919 FOREIGN PATENTS Country Date Great Britain Oct. 24, 1904 

